1. Field of the Invention
The present invention relates to a molding die structure of a molded article and a manufacturing method of a molded article for injecting a molding material in cavities formed between two dies separated by a parting line and molding a molded article.
2. Description of the Related Art
In general, for example, a small lens or the like used in a digital camera, an endoscope, a microscope, a mobile phone, and others is manufactured by cavity forming using a resin. As a molding die structure in the cavity forming, a cavity is formed between two dies separated by a parting line. This cavity is filled with a heated and softened thermoplastic material or an energy curing material. As a result, a lens having a highly precise shape is provided. In this case, for example, the lens has two optical surfaces. In lenses of recent years, a smaller displacement of a center position between two optical surfaces (which will be referred to as an eccentricity accuracy hereinafter) is demanded in particular. In lenses molded by injection molding, a technology that improves the eccentricity accuracy of lenses is disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2008-183754. In a molding die structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2008-183754, two dies separated by a parting line accommodate two molding dies that are used for molding and transferring two optical surfaces of a lens therein. Here, since the two dies are combined in advance and the two dies are subjected to machining at the same time, hole portions that serve as accommodating portions that accommodate the two molding dies are formed. Then, when the molding dies are press-fitted into the hole portions, an axial displacement of the molding dies is improved. As a result, the eccentricity accuracy of the lens is improved.
Further, for example, in Japanese Patent No. 3485562, a ball retainer is provided between a molding die and a die. As a result, a clearance between the molding die and the die in a radial direction is reduced, and the two dies are taper-fitted, thereby improving an axial displacement of the molding die.